wget will pick up a dl where it left off. i know that "pick up where you left off" capability has been built into HTTP since the mid '90s if not right from scratch
i used to use that feature to run several downloads from several different sites of different sections of linux distro isos when new releases were put up
i used to use that feature to run several downloads from several different sites of different sections of linux distro isos when new releases were put up